Implantable hearing devices stimulate internal components of the auditory system and are generally classified into one of two types, namely fully implantable hearing aids and semi-implantable hearing aids. In a fully implantable hearing device, the entire device is implanted. In a semi-implantable hearing device, some of the components, typically the microphone, power supply, and speech signal processor, are externally worn, while the transducer/stimulator and key support functions are implanted within the auditory system. The externally worn portion communicates transcutaneously with the implanted portion to provide audio signals that the implanted portion uses to stimulate to the auditory system.
By way of example, one type of implantable transducer includes an electromechanical transducer having a magnetic coil that drives a vibratory actuator. The actuator is positioned to interface with and stimulate the ossicular chain of the patient via physical engagement. (See e.g., U.S. Pat. No. 5,702,342). In this regard, one or more bones of the ossicular chain are made to mechanically vibrate, which causes the ossicular chain to stimulate the cochlea through its natural input, the so-called oval window.
Implanted hearing devices are typically used by individuals with significant loss of hearing function or damage to the auditory system. As a result, they differ in the manner by which the signal is processed and delivered to the patient. The processing step, known in the art as Speech Signal Processing (“SSP”), may include a number of steps such as amplification, frequency shaping, compression, etc. The steps in the SSP are determined by the design of the hearing device, while the particular internal values used in the steps are generated from prescriptive parameters determined by an audiologist. Once a speech processor receives an audio signal (e.g., from a microphone) that is indicative of ambient acoustic signals, an drive signal produced and provided to an implanted stimulation device that stimulates the hearing impaired person's auditory system. The auditory stimulation may be done acoustically, mechanically, or electrically as a function of the type and severity of the hearing loss in the hearing impaired individual.
The type and/or severity of hearing loss may dictate what type of implantable hearing device may be beneficial to an impaired person. Heretofore, this has required that many impaired persons utilize semi-implantable hearing devices. Some surveys of current and potential hearing instrument wearers show that fully implantable or non-visible hearing devices have greater consumer acceptance. That is, there is some belief that fully implantable hearing devices may avoid stigmatizing cosmetics associated with semi-implantable devices.